Recently, a shadow area in which a propagation environment for wireless communication systems such as GSM/PCS/3G/4G is poor has been generated inside buildings as structures of high-story buildings and inner spaces thereof have become more complicated. Accordingly, technologies to solve this problem are needed. To improve propagation environments, a technology using a relay or a technology using a micro base station are used.
The technology using a relay improves propagation environments using two antennas and an active relay which is provided between the two antennas and uses a bidirectional amplification circuit or a passive relay which connects the two antennas through a coaxial cable or a waveguide. Specifically, an antenna is installed outside a building, in which a propagation environment is satisfactory, and connected to a waveguide or a coaxial cable and the waveguide or coaxial cable is connected to an antenna installed in a shadow area inside the building, thereby improving the propagation environment of the shadow area.
The technology using a micro base station improves the propagation environment and coverage of wireless communication using a micro base station such as a pico cell base station or a femto cell base station installed inside a building.
However, the technology using a relay or a micro base station requires high costs to solve ail shadow areas and needs new equipment for band expansion of wireless communication. Furthermore, an external propagation signal and a relayed internal propagation signal overlap in as inside area or a building, which is adjacent to glass windows. Terminals connected to the corresponding wireless communication system may be unintentionally exposed to multi-path fading doe to the aforementioned propagation signal overlap.
Accordingly, it is necessary to develop an antenna capable of contributing to expansion of the coverage of a wireless communication system without generating the aforementioned problem and operating in a wide frequency band.
The present invention has been made to satisfy the aforementioned technical requirements and solves the above-described problems and provides techniques that cannot be easily developed by a person skilled in the art.